1. Field of the Invention
The present invention generally concerns alleviating displaced first-printed characters on single-part forms, and light characters on multi-part forms, due to the energy loss incurred in forms compression by that print hammer(s) first printing upon each line in an impact printer. The invention specifically concerns boosting the hammer drive current for the first print hammer(s) actuated in the printing of each line by an impact printer.
2. Description of the Prior Art
There exists a problem with the print quality of an impact printer, most particularly a band printer but also any printer such as a drum printer, wherein a hammer strikes a form to press such form against a type font disposed proximate to such form and oppositely to the hammer, thereby printing the character of such type font. This problem with an impact printer, particularly visible on multipart forms, resides in the fact that the first hammer(s) fired upon each print line must compress the forms paper, and thus dissipate energy which would otherwise be used in the generation of the printed character. The result of this energy loss is a light character on multi-part forms, or a displaced character on single-part forms. The displaced character problem is most noticeably visible for characters having a strong vertical line component, such as a "H" or "F", when such characters repetitively appear in the same print position, or column, of many lines upon a printed form. When certain ones of the characters, in certain lines, are printed by first, or early, hammers fired in the printing of such lines whereas others of the characters, in other lines, are printed by later-fired hammers then the problem is manifested. The problem is noticeable as a "ragged", non-aligned, appearance of the characters in the print columns. The problem is so widely prevalent and recognized that it has an ascribed name: "the first hammer out problem", meaning that the problem is resultant from a condition occurring with the first actuated print hammers upon each print line.
The traditional, prior art, method of attempting to deal with that first hammer out problem which results in displaced and/or light characters in the print line printed by an impact printer is to attempt to better mechanically compress the form. Mechanical forms compressors have been used, which can either be passive-type compression fingers or active-type devices such as electronically controlled clamps which are enabled only during printing. The disadvantages of these mechanical forms compression methods are many. For the simpler and more rudimentary methods where the form is continually compressed, as by passive-type compression fingers, such compression may be in conflict with the reliable and rapid movement of the form through the printer in the printing of successive lines. The active-type compression devices, which may only attempt to compress the form simultaneous with the printing of each line and release compression during forms movement, are expensive and unreliable. Further, both methods must operate at some distance from the actual strike point of the print hammer upon the form, and are thus necessarily imperfect in securing the optimal forms registration and compression at that very point(s) which counts most, the point(s) opposite the first striking print hammer(s) wherein the first character(s) will be printed upon each print line. Finally, it should be recognized that any mechanical forms compression system separate from the remaining operative parts, and core functionality, of the printer will have negative cost and reliability implications to the implementation of the basic printer function which is simply to print.